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| <title>LLVM 1.8 Release Notes</title> |
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| <body> |
| |
| <div class="doc_title">LLVM 1.8 Release Notes</div> |
| |
| <ol> |
| <li><a href="#intro">Introduction</a></li> |
| <li><a href="#whatsnew">What's New?</a></li> |
| <li><a href="GettingStarted.html">Installation Instructions</a></li> |
| <li><a href="#portability">Portability and Supported Platforms</a></li> |
| <li><a href="#knownproblems">Known Problems</a> |
| <li><a href="#additionalinfo">Additional Information</a></li> |
| </ol> |
| |
| <div class="doc_author"> |
| <p>Written by the <a href="http://llvm.org">LLVM Team</a><p> |
| </div> |
| |
| <!-- *********************************************************************** --> |
| <div class="doc_section"> |
| <a name="intro">Introduction</a> |
| </div> |
| <!-- *********************************************************************** --> |
| |
| <div class="doc_text"> |
| |
| <p>This document contains the release notes for the LLVM compiler |
| infrastructure, release 1.8. Here we describe the status of LLVM, including any |
| known problems and major improvements from the previous release. The most |
| up-to-date version of this document (corresponding to LLVM CVS) can be found |
| on the <a |
| href="http://llvm.org/releases/">LLVM releases web site</a>. If you are |
| not reading this on the LLVM web pages, you should probably go there because |
| this document may be updated after the release.</p> |
| |
| <p>For more information about LLVM, including information about the latest |
| release, please check out the <a href="http://llvm.org/">main LLVM |
| web site</a>. If you have questions or comments, the <a |
| href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing |
| list</a> is a good place to send them.</p> |
| |
| <p>Note that if you are reading this file from CVS or the main LLVM web page, |
| this document applies to the <i>next</i> release, not the current one. To see |
| the release notes for the current or previous releases, see the <a |
| href="http://llvm.org/releases/">releases page</a>.</p> |
| |
| </div> |
| |
| <!-- *********************************************************************** --> |
| <div class="doc_section"> |
| <a name="whatsnew">What's New?</a> |
| </div> |
| <!-- *********************************************************************** --> |
| |
| <div class="doc_text"> |
| |
| <p>This is the ninth public release of the LLVM Compiler Infrastructure. This |
| release incorporates a large number of enhancements and new features, |
| including DWARF debugging support (C and C++ on Darwin/PPC), improved inline |
| assembly support, a new <a href="http://llvm.org/nightlytest/">nightly |
| tester</a>, llvm-config enhancements, many bugs |
| fixed, and performance and compile time improvements. |
| </p> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="newfeatures">New Features in LLVM 1.8</a> |
| </div> |
| |
| <!--_________________________________________________________________________--> |
| <div class="doc_subsubsection"><a name="dwarf">DWARF debugging |
| support </a></div> |
| |
| <div class="doc_text"> |
| |
| <p>The llvm-gcc4 C front-end now generates debugging info for C and C++. This |
| information is propagated through the compiler and the code generator can |
| currently produce DWARF debugging information from it. DWARF is a standard |
| debugging format used on many platforms, but currently LLVM only includes |
| target support for Mac OS X targets for the 1.8 release. |
| </p> |
| |
| </div> |
| |
| <!--_________________________________________________________________________--> |
| <div class="doc_subsubsection"><a name="inlineasm">Inline Assembly |
| Support</a></div> |
| |
| <div class="doc_text"> |
| |
| <p>Inline assembly support is substantially improved in LLVM 1.8 over LLVM 1.7. |
| Many unsupported features are now supported, and inline asm support in the X86 |
| backend is far better. llvm-gcc4 now supports global register variables as |
| well.</p> |
| |
| </div> |
| |
| <!--_________________________________________________________________________--> |
| <div class="doc_subsubsection"><a name="loopopt">Loop Optimizer Improvements</a></div> |
| |
| <div class="doc_text"> |
| |
| <p>The loop optimizer passes now uses "Loop-Closed SSA Form", which makes it |
| easier to update SSA form as loop transformations change the code. An |
| immediate benefit of this is that the loop unswitching pass can now unswitch |
| loops in more cases. |
| </p> |
| |
| </div> |
| |
| <!--_________________________________________________________________________--> |
| <div class="doc_subsubsection"><a name="jumptab">Jump Table Support for Switches |
| </a></div> |
| |
| <div class="doc_text"> |
| |
| <p>The code generator now lowers switch statements to jump tables, providing |
| significant performance boosts for applications (e.g. interpreters) whose |
| performance is highly correlated to switch statement performance.</p> |
| |
| </div> |
| |
| <!--_________________________________________________________________________--> |
| <div class="doc_subsubsection"><a name="jitrelease">Deallocation of JIT'd |
| Machine Code |
| </a></div> |
| |
| <div class="doc_text"> |
| |
| <p>The LLVM JIT now allows clients to deallocate machine code JIT'd to its code |
| buffer. This is important for long living applications that depend on the JIT. |
| </p> |
| |
| </div> |
| |
| <!--_________________________________________________________________________--> |
| <div class="doc_subsubsection"><a name="other">Other Improvements</a></div> |
| |
| <div class="doc_text"> |
| |
| <p>This release includes many other improvements, including improvements to |
| the optimizers and code generators (improving the generated code) changes to |
| speed up the compiler in many ways (improving algorithms and fine tuning |
| code), and changes to reduce the code size of the compiler itself.</p> |
| |
| <p>More specific changes include:</p> |
| |
| <ul> |
| <li>LLVM 1.8 includes an initial ARM backend. This backend is in early |
| development stages.</li> |
| <li>LLVM 1.8 now includes significantly better support for mingw and |
| cygwin.</li> |
| <li>The <a href="CommandGuide/html/llvm-config.html">llvm-config</a> tool is |
| now built by default and has several new features.</li> |
| <li>The X86 and PPC backends now use the correct platform ABI for passing |
| vectors as arguments to functions.</li> |
| <li>The X86 backend now includes support for the Microsoft ML assembler |
| ("MASM").</li> |
| <li>The PowerPC backend now pattern matches the 'rlwimi' instruction more |
| aggressively.</li> |
| <li>Most of LLVM is now built with "-pedantic", ensuring better portability |
| to more C++ Compilers.</li> |
| <li>The PowerPC backend now includes initial 64-bit support. The JIT is not |
| complete, and the static compiler has a couple of known bugs, but support |
| is mostly in place. LLVM 1.9 will include completed PPC-64 support. </li> |
| |
| </ul> |
| </div> |
| |
| <!--=========================================================================--> |
| <div class="doc_subsection"> |
| <a name="changes">Significant Changes in LLVM 1.8</a> |
| </div> |
| |
| <div class="doc_text"> |
| <ul> |
| <li>The LLVM "SparcV9" backend (deprecated in LLVM 1.7) has been removed in |
| LLVM 1.8. The LLVM "Sparc" backend replaces it.</li> |
| <li>The --version option now prints more useful information, including the |
| build configuration for the tool.</li> |
| </ul> |
| </div> |
| |
| |
| <!-- *********************************************************************** --> |
| <div class="doc_section"> |
| <a name="portability">Portability and Supported Platforms</a> |
| </div> |
| <!-- *********************************************************************** --> |
| |
| <div class="doc_text"> |
| |
| <p>LLVM is known to work on the following platforms:</p> |
| |
| <ul> |
| <li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD |
| (and probably other unix-like systems).</li> |
| <li>Intel and AMD machines running on Win32 using MinGW libraries (native)</li> |
| <li>Sun UltraSPARC workstations running Solaris 8.</li> |
| <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited |
| support is available for native builds with Visual C++).</li> |
| <li>PowerPC and X86-based Mac OS X systems, running 10.2 and above.</li> |
| <li>Alpha-based machines running Debian GNU/Linux.</li> |
| <li>Itanium-based machines running Linux and HP-UX.</li> |
| </ul> |
| |
| <p>The core LLVM infrastructure uses |
| <a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself |
| to the machine and operating system on which it is built. However, minor |
| porting may be required to get LLVM to work on new platforms. We welcome your |
| portability patches and reports of successful builds or error messages.</p> |
| |
| </div> |
| |
| <!-- *********************************************************************** --> |
| <div class="doc_section"> |
| <a name="knownproblems">Known Problems</a> |
| </div> |
| <!-- *********************************************************************** --> |
| |
| <div class="doc_text"> |
| |
| <p>This section contains all known problems with the LLVM system, listed by |
| component. As new problems are discovered, they will be added to these |
| sections. If you run into a problem, please check the <a |
| href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if |
| there isn't already one.</p> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="experimental">Experimental features included with this release</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>The following components of this LLVM release are either untested, known to |
| be broken or unreliable, or are in early development. These components should |
| not be relied on, and bugs should not be filed against them, but they may be |
| useful to some people. In particular, if you would like to work on one of these |
| components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p> |
| |
| <ul> |
| <li>The <tt>-cee</tt> pass is known to be buggy, and may be removed in in a |
| future release.</li> |
| <li>The IA64 code generator is experimental.</li> |
| <li>The Alpha JIT is experimental.</li> |
| <li>"<tt>-filetype=asm</tt>" (the default) is the only supported value for the |
| <tt>-filetype</tt> llc option.</li> |
| </ul> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="build">Known problems with the Build System</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ul> |
| <li>none yet</li> |
| </ul> |
| </div> |
| |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="core">Known problems with the LLVM Core</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ul> |
| <li>In the JIT, <tt>dlsym()</tt> on a symbol compiled by the JIT will not |
| work.</li> |
| </ul> |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="c-fe">Known problems with the C front-end</a> |
| </div> |
| |
| <!-- _______________________________________________________________________ --> |
| <div class="doc_subsubsection">Bugs</div> |
| |
| <div class="doc_text"> |
| |
| <p> |
| llvm-gcc3 has many significant problems that are fixed by llvm-gcc4. |
| Two major ones include:</p> |
| |
| <ul> |
| <li>With llvm-gcc3, |
| C99 variable sized arrays do not release stack memory when they go out of |
| scope. Thus, the following program may run out of stack space: |
| <pre> |
| for (i = 0; i != 1000000; ++i) { |
| int X[n]; |
| foo(X); |
| } |
| </pre></li> |
| |
| <li>With llvm-gcc3, Initialization of global union variables can only be done <a |
| href="http://llvm.org/PR162">with the largest union member</a>.</li> |
| |
| </ul> |
| |
| <p>llvm-gcc4 is far more stable and produces better code than llvm-gcc3, but |
| does not currently support Link-Time-Optimization or C++ Exception Handling, |
| which llvm-gcc3 does.</p> |
| |
| </div> |
| |
| <!-- _______________________________________________________________________ --> |
| <div class="doc_subsubsection"> |
| Notes |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ul> |
| |
| <li>"long double" is transformed by the front-end into "double". There is no |
| support for floating point data types of any size other than 32 and 64 |
| bits.</li> |
| |
| <li>The following Unix system functionality has not been tested and may not |
| work: |
| <ol> |
| <li><tt>sigsetjmp</tt>, <tt>siglongjmp</tt> - These are not turned into the |
| appropriate <tt>invoke</tt>/<tt>unwind</tt> instructions. Note that |
| <tt>setjmp</tt> and <tt>longjmp</tt> <em>are</em> compiled correctly. |
| <li><tt>getcontext</tt>, <tt>setcontext</tt>, <tt>makecontext</tt> |
| - These functions have not been tested. |
| </ol></li> |
| |
| <li>Although many GCC extensions are supported, some are not. In particular, |
| the following extensions are known to <b>not be</b> supported: |
| <ol> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nested%20Functions">Nested Functions</a>: As in Algol and Pascal, lexical scoping of functions.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#Extended%20Asm">Extended Asm</a>: Assembler instructions with C expressions as operands.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Asm-Labels.html#Asm%20Labels">Asm Labels</a>: Specifying the assembler name to use for a C symbol.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Explicit-Reg-Vars.html#Explicit%20Reg%20Vars">Explicit Reg Vars</a>: Defining variables residing in specified registers.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html#Vector%20Extensions">Vector Extensions</a>: Using vector instructions through built-in functions.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Target-Builtins.html#Target%20Builtins">Target Builtins</a>: Built-in functions specific to particular targets.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li> |
| </ol> |
| |
| <p>The following GCC extensions are <b>partially</b> supported. An ignored |
| attribute means that the LLVM compiler ignores the presence of the attribute, |
| but the code should still work. An unsupported attribute is one which is |
| ignored by the LLVM compiler and will cause a different interpretation of |
| the program.</p> |
| |
| <ol> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>: |
| Arrays whose length is computed at run time.<br> |
| Supported, but allocated stack space is not freed until the function returns (noted above).</li> |
| |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>: |
| |
| Declaring that functions have no side effects or that they can never |
| return.<br> |
| |
| <b>Supported:</b> <tt>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>, |
| <tt>noreturn</tt>, <tt>constructor</tt>, <tt>destructor</tt>, |
| <tt>unused</tt>, <tt>used</tt>, |
| <tt>deprecated</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br> |
| |
| <b>Ignored:</b> <tt>noinline</tt>, |
| <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>, |
| <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br> |
| |
| <b>Unsupported:</b> <tt>section</tt>, <tt>alias</tt>, |
| <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>, |
| <tt>fastcall</tt>, all other target specific attributes</li> |
| |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>: |
| Specifying attributes of variables.<br> |
| <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>, |
| <tt>deprecated</tt>, <tt>transparent_union</tt>, |
| <tt>unused</tt>, <tt>used</tt>, <tt>weak</tt><br> |
| |
| <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>, |
| <tt>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>, |
| <tt>vector_size</tt>, <tt>dllimport</tt>, |
| <tt>dllexport</tt>, all target specific attributes.</li> |
| |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br> |
| <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>, |
| <tt>deprecated</tt>, <tt>may_alias</tt><br> |
| |
| <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>, |
| all target specific attributes.</li> |
| |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>: |
| Other built-in functions.<br> |
| We support all builtins which have a C language equivalent (e.g., |
| <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>, |
| <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>, |
| <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt> |
| (currently ignored). We also support builtins for ISO C99 floating |
| point comparison macros (e.g., <tt>__builtin_islessequal</tt>), |
| <tt>__builtin_prefetch</tt>, <tt>__builtin_popcount[ll]</tt>, |
| <tt>__builtin_clz[ll]</tt>, and <tt>__builtin_ctz[ll]</tt>.</li> |
| </ol> |
| |
| <p>The following extensions <b>are</b> known to be supported:</p> |
| |
| <ol> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html#Labels%20as%20Values">Labels as Values</a>: Getting pointers to labels and computed gotos.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Typeof.html#Typeof">Typeof</a>: <code>typeof</code>: referring to the type of an expression.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc-3.4.0/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variadic-Macros.html#Variadic%20Macros">Variadic Macros</a>: Macros with a variable number of arguments.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Subscripting.html#Subscripting">Subscripting</a>: Any array can be subscripted, even if not an lvalue.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pointer-Arith.html#Pointer%20Arith">Pointer Arith</a>: Arithmetic on <code>void</code>-pointers and function pointers.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions, |
| or arrays as values.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Cast-to-Union.html#Cast%20to%20Union">Cast to Union</a>: Casting to union type from any member of the union.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Comments.html#C_002b_002b-Comments">C++ Comments</a>: C++ comments are recognized.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Character-Escapes.html#Character%20Escapes">Character Escapes</a>: <code>\e</code> stands for the character <ESC>.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alternate-Keywords.html#Alternate%20Keywords">Alternate Keywords</a>:<code>__const__</code>, <code>__asm__</code>, etc., for header files.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Incomplete-Enums.html#Incomplete%20Enums">Incomplete Enums</a>: <code>enum foo;</code>, with details to follow.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Names.html#Function%20Names">Function Names</a>: Printable strings which are the name of the current function.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Return-Address.html#Return%20Address">Return Address</a>: Getting the return or frame address of a function.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html#Unnamed%20Fields">Unnamed Fields</a>: Unnamed struct/union fields within structs/unions.</li> |
| <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li> |
| </ol></li> |
| |
| </ul> |
| |
| <p>If you run into GCC extensions which have not been included in any of these |
| lists, please let us know (also including whether or not they work).</p> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="c++-fe">Known problems with the C++ front-end</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>For this release, the C++ front-end is considered to be fully |
| tested and works for a number of non-trivial programs, including LLVM |
| itself.</p> |
| |
| </div> |
| |
| <!-- _______________________________________________________________________ --> |
| <div class="doc_subsubsection">Bugs</div> |
| |
| <div class="doc_text"> |
| |
| <ul> |
| <li>The C++ front-end inherits all problems afflicting the <a href="#c-fe">C |
| front-end</a>.</li> |
| |
| </ul> |
| |
| </div> |
| |
| <!-- _______________________________________________________________________ --> |
| <div class="doc_subsubsection"> |
| Notes |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ul> |
| |
| <li>Destructors for local objects are not always run when a <tt>longjmp</tt> is |
| performed. In particular, destructors for objects in the <tt>longjmp</tt>ing |
| function and in the <tt>setjmp</tt> receiver function may not be run. |
| Objects in intervening stack frames will be destroyed, however (which is |
| better than most compilers).</li> |
| |
| <li>The LLVM C++ front-end follows the <a |
| href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>. |
| This document, which is not Itanium specific, specifies a standard for name |
| mangling, class layout, v-table layout, RTTI formats, and other C++ |
| representation issues. Because we use this API, code generated by the LLVM |
| compilers should be binary compatible with machine code generated by other |
| Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc). |
| <i>However</i>, the exception handling mechanism used by LLVM is very |
| different from the model used in the Itanium ABI, so <b>exceptions will not |
| interact correctly</b>. </li> |
| |
| </ul> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="c-be">Known problems with the C back-end</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ul> |
| |
| <li>The C back-end produces code that violates the ANSI C Type-Based Alias |
| Analysis rules. As such, special options may be necessary to compile the code |
| (for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This |
| problem probably cannot be fixed.</li> |
| |
| <li><a href="http://llvm.org/PR56">Zero arg vararg functions are not |
| supported</a>. This should not affect LLVM produced by the C or C++ |
| frontends.</li> |
| |
| <li>The C backend does not correctly implement the <a |
| href="LangRef.html#i_stacksave"><tt>llvm.stacksave</tt></a> or |
| <a href="LangRef.html#i_stackrestore"><tt>llvm.stackrestore</tt></a> |
| intrinsics. This means that some code compiled by it can run out of stack |
| space if they depend on these (e.g. C99 varargs).</li> |
| |
| </ul> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="x86-be">Known problems with the X86 back-end</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ul> |
| <li>none yet.</li> |
| </ul> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="ppc-be">Known problems with the PowerPC back-end</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ul> |
| <li><a href="http://llvm.org/PR642">PowerPC backend does not correctly |
| implement ordered FP comparisons</a>.</li> |
| </ul> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="alpha-be">Known problems with the Alpha back-end</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ul> |
| |
| <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the |
| appropriate nops inserted to ensure restartability.</li> |
| |
| </ul> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="ia64-be">Known problems with the IA64 back-end</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ul> |
| |
| <li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are |
| made where the argument is not 16-byte aligned, as required on IA64. (Strictly |
| speaking this is not a bug in the IA64 back-end; it will also be encountered |
| when building C++ programs using the C back-end.)</li> |
| |
| <li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64 |
| ABI compliant layout of v-tables</a>. In particular, it just stores function |
| pointers instead of function descriptors in the vtable. This bug prevents |
| mixing C++ code compiled with LLVM with C++ objects compiled by other C++ |
| compilers.</li> |
| |
| <li>There are a few ABI violations which will lead to problems when mixing LLVM |
| output with code built with other compilers, particularly for floating-point |
| programs.</li> |
| |
| <li>Defining vararg functions is not supported (but calling them is ok).</li> |
| |
| </ul> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="sparc-be">Known problems with the SPARC back-end</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ul> |
| <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not |
| support the 64-bit SPARC ABI (-m64).</li> |
| </ul> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="arm-be">Known problems with the ARM back-end</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ul> |
| <li>The ARM backend is currently in early development stages, it is not |
| ready for production use.</li> |
| </ul> |
| |
| </div> |
| |
| <!-- *********************************************************************** --> |
| <div class="doc_section"> |
| <a name="additionalinfo">Additional Information</a> |
| </div> |
| <!-- *********************************************************************** --> |
| |
| <div class="doc_text"> |
| |
| <p>A wide variety of additional information is available on the <a |
| href="http://llvm.org">LLVM web page</a>, including <a |
| href="http://llvm.org/docs/">documentation</a> and <a |
| href="http://llvm.org/pubs/">publications describing algorithms and |
| components implemented in LLVM</a>. The web page also contains versions of the |
| API documentation which is up-to-date with the CVS version of the source code. |
| You can access versions of these documents specific to this release by going |
| into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p> |
| |
| <p>If you have any questions or comments about LLVM, please feel free to contact |
| us via the <a href="http://llvm.org/docs/#maillist"> mailing |
| lists</a>.</p> |
| |
| </div> |
| |
| <!-- *********************************************************************** --> |
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